In recent years, liquid crystals have been used in a variety of devices; in particular, liquid crystal display devices (liquid crystal displays) having advantages of thinness and lightness have been used for displays in a wide range of fields.
Low power consumption is an added value required of a liquid crystal display device. For example, in an active matrix liquid crystal display device, a transistor with low off-state current is used as a transistor having a function of applying voltage to a liquid crystal element; thus, data is rewritten at longer time intervals (a refresh rate is reduced) in a period during which one image (still image) is displayed, and power consumption is reduced (Patent Document 1).